Biologic potential of rare pigmented epithelioid melanocytome remains unclear
A recent study shows that pigmented epithelioid melanocytome (PEM) tends to exhibit an indolent behaviour, but current evidence is too limited to provide insight into its true biologic potential.
Researchers probed the pathology database for cases of PEM diagnosed at the University of Rochester and reviewed charts for follow-up information. In two cases, multinational analysis of melanoma-associated genes was conducted.
A 10-year retrospective review yielded nine cases of PEM. There were five patients who underwent sentinel lymph node biopsy, of whom three had a positive sentinel lymph node. All nine patients are alive and disease-free, with average 38.75 months of follow-up.
Two tumours were examined for common melanoma-related mutations. The samples tested negative, except for a telomerase reverse transcriptase promoter deletion detected in one tumour. Such deletion did not correlate with melanoma; thus, its biologic significance remains unclear.
The findings of this study should be interpreted in light of its limitations, which included a small sample size, a retrospective design and a single institution experience, according to researchers.
A recently described entity with unknown biologic behaviour, PEM is a rare, heavily pigmented, borderline, melanocytic tumour with infiltrative borders, which has potential for frequent metastases but shows an indolent clinical course. Epithelioid and spindled melanocytes with heavy pigmentation comprise these tumours. [Eplasty 2016;16;16:e33]
A Japan study presented in 2009 reported PEM cases that might have been previously diagnosed as cellular blue nevus. Researchers suggested that Japanese pathologists must recognize a new concept of PEM, which should be recommended sentinel lymph node sampling when they make such a diagnosis. [J Cutan Pathol 2009;36:439-43]